Electric controlling apparatus



May 29, 1951 R. A. ANDREWS ELECTRIC commune APPARATUS 2 Sheets-Sheet 1Filed March 5, 1947 KSJ y 1951 R. A. ANDREWS 2,555,103

ELECTRIC CONTROLING APPARATUS Filed March 5, 1947 2 SheetsSheet 2INVENTOR. lia -vs /9. fl/mms'ms Patented May 29, 1951 ELECTRICCONTROLLING APPARATUS Rufus A. Andrews, Mamaroneck, N. Y., assignor toWard Leonard Electric Company, a corporation of New York ApplicationMarch 5, 1947, Serial No. 732,421

6 Claims.

This invention relates to improvements in variable voltage devices andparticularly in variable voltage transformers wherein the voltage isvariable in small steps from the maximum voltage to zero voltage. Thisinvention is an improvement over the disclosures in the pendingapplication of Frank G. Logan, Serial No. 593,344, filed May 12, 1945,now Patent Number 2,515,782.

One object of the present invention is to provide a unitary structurewhich will dissipate the heat readily from the winding, from the contactsegments and from resistors connected between the winding and thesegments. Another object is to provide and locate resistors connectedbetween the segments and the winding so that not only will the heat befreely dissipated therefrom but will form part of the unitarytransformer structure and permit the use of low resistance brushes.Other objects and advantages will be understood from the followingdescription and accompanying drawings showing a preferred emshowing thebrush holder assembly; Fig. 4 is an end view of Fig.3; and Fig. 5 is asection on the line 55 of Fig. 1 showing the contact assembly of thecontacts engaging the fixed collector ring.

Referring to Fig. 2 a circular iron core 6 is of laminated form with thelaminations extending in an axial direction and built up by winding aribbon of iron or steel on itself from the inner diameter of the core tothe outer diameter. The core is covered with a winding of insulatingtape. The winding 7 on the core, which may be of glass insulated copperwire of square section, or other form, covers the core except a smallsection at the top. The inside and outside dimensions of the core arepreferably selected so that the portions of the turns on the inside ofthe core are bank wound while those portions on the outside of the coreare adjacent to each other and form a single layer.

The fixed contact segments 8 are in the form of radial outwardlyextending long wedge-shaped strips, preferably of hard brass. As shownin Fig. 2, they have an elongated main contact portion with an outer endportion 8a extending forwardly and a portion 8b at right-angles theretoextending outwardly. At the inner end of the segment, a portion 80extends forwardly. The tapered form of the faces of the segments andtheir radially extending edges insure that all of the brushes may makecontact with each segment substantially simultaneously as the brushesare advanced to a higher voltage contact segment. The contact segmentsare electrically connected to every other turn of the winding in theform shown although they may be connected to successive turns in somecases or to every third turn, etc.

Each segment is electrically connected to its respective turn of thewinding through a resistor 9, as shown in Fig. 2. This is preferably anarrow thin strip of resistive metal, such as a copper nickel alloy, andis corrugated as shown for obtaining a sufficiently high resistance. Theouter flat end of the resistor is silver soldered to the front face ofthe outer end of the segment. The inner end of each resistor is silversoldered to its respective turn of the winding after removal ofinsulation from those portions of the winding Where the connections aremade. The connection of the resistors to the Winding is facilitated bycausing portions of the winding to project from the main portion. Thusas shown in Fig. 2, a portion of the turn "la projects outwardly and aportion of the next turn lb to which a segment is to be connectedprojects forwardly at a front corner of the winding. These projectingportions of the winding may be formed by use of removable pins overwhich the projecting portions are wound during the process of winding.

The transformer unit is carried and supported by a circular dished baseplate [0 covering the front of the apparatus and having a rim whichprojects rear wardly. This plate may be of sheet steel or sheet brassand is shaped to conform to the required support and protection of theparts. At the center of the plate is fixed a metal cup-shaped piece IIwith its open end at the rear. Adhesive insulating material l2, such ascement, fills the space between the base plate and the winding up to therim of the cup or retainer ll, embedding about half of the Winding,fully embedding the resistors 9, and likewise embedding the segments 8up to near their faces and filling the spaces between the segments. Whenthe embedding material is matured, it firmly supports the segments infixed position, the forwardly extending legs 8a, 8b and 8c of thesegments being covered. It likewise holds the resistors 9 in fixedposition and similarly supports the winding. The embedding insulationalso serves to effectively and efiiciently conduct the heat from thewinding, the contact segments and the resistors mainly to the metal baseplate where it is dissipated to the air over its exposed front face andrim. The open cup, or retainer II, also aids in dissipation of the heatto its open central space.

The drive shaft l3 extends axially through the base plate and cup II andis provided with a pulley l4 coupled to the shaft by a removable crosspin l4a for actuation of the contact arm, or a removable handle may befixed to the front end of the shaft for that purpose. A metal strip I5is shown fixed within end slots of the pulley by the end nut [41), thestrip extending horizontally in the position shown and has a pair offorwardly projecting ends l5a to form a coupling with other similarapparatus when several of them are banked for simultaneous operation. Aplate 7 I6 is fixed to the inner end of the pulley over projecting endportions and in the position shown extends upwardly to engage a stop I1a which projects forwardly from a plate I! fixed to the base plate. Theshaft is journaled in a pair of oilless type bushings l8, one at thefront portion of the shaft and one at the rear portion. A hearing sleeveor hearing hub l9 encloses the bushings and has an outwardly extendingbead |9a which seats against the central portion of the cup H. The frontend Nb of the bearing sleeve is turned outwardly to engage the centralpart of the stop plate IT. The sleeve is thus held in fixed position. Athrust bearing washer 2!! is interposed between the plates l6 and i1. Onthe inner portion of the bearing sleeve is mounted the collector ringhub 2| of moulded insulation material. It is held in fixed position by apin 22, the rear end of which projects within an opening in the hub andthe front end of which is riveted over the face of the plate H. A metalspacing sleeve 23 extends between the hub and the central portion of thecup II and bears on the bead 19a. A reduced portion of the hub extendsrearwardly and on this is mounted the collector ring plate 24,preferably of brass. It is secured to the enlarged portion of the hub byangularly spaced screws 24a.

On the top of the rim. of the base plate is mounted a terminal block 25of moulded insulating material. Near its two ends are mounted upwardlyextending terminal bolts 26, the heads of the bolts being moulded Withinthe terminal block. A hole is formed in the block at the inner side ofeach terminal bolt. One free end Tc of the winding 1 passes from thewinding through the embedding insulation l2, then out near the hole inthe terminal block, then through the hole to its terminal bolt. Theother free end 10 of the winding similarly extends to the other terminalbolt. A terminal washer 21 of moulded insulating material is positionedon the inside of the rim of the base plate and has an upwardly extendingportion which passes through the rim and within an opening in the lowercentral portion of the terminal block, as well shown in Fig. 2. Athrough terminal bolt 28 passes through the terminal block and washer 21and serves to clamp the block in fixed position on the rim. This boltserves as one terminal to which the load is connected,

I the other terminal of the load being connected to one of the bolts 26.A terminal lead 29 in the form of a fiat copper strip is secured at itsupper end to the terminal bolt 28 and then passes downwardly over thecore 6 to the collector ring 24 and is silver soldered to the upper partof the ring on its front side.

The contact arm 30 is preferably of brass for magnetic reasons and forgood conductivity and 3 lb by which it is fastened by screws to theunder side of the contact arm. At the lower portion of the open side ofthe holder is secured by welding a sheet metal brush guide plate 34. Six

\ brushes 32 are shown positioned in the holder within this guide plateso as to be freely movable therein, or any other appropriate number ofbrushes may be used. The guide plate is provided with six verticallyextending slots opposite the brushes respectively, these slots beingopen at the top. Flexible pig-tail leads 35 are connected to the brushesrespectively at one end, then pass through the slots of the guide plate,then under the contact arm and over the extended edge of the terminalplate 33, then down through six holes in this plate to its under sidewhere the ends are silver soldered to the plate. During the wear of thebrushes, their pig-tail leads pass respectively within the slots in theguide plate. The side of the brush holder is provided with holes 310 forthe circulation of cooling air. Each brush is individually pressedagainst the contact segments by its coiled spring 36 which seats at oneend on the top of its brush around a projection on the brush and at itsother end against the inner side of the terminal plate. Eyelets 31 arefixed in the terminal plate at their outer ends and project inwardlywithin the ends of the springs 36 opposite each brush respectively, andserve to position and guide the springs and also to prevent the brushesfrom moving up so far as to be dislodged from the holder. The brushholder and terminal plate are fixed at their ends to the contact arm byscrews 38, giving good electrical surface contact therewith. The sideextension 3lb of the brush holder is secured to the contact arm by thescrew 38a.

The electrical connection from the contact arm to the collector ring 24is made by two contact assemblies on opposite sides of the center lineof the contact arm, as shown in Fig. 1, each contact assembly beingspaced a considerable distance from the center line. The detail of eachof these contact assemblies is shown in Fig. 5. The con tact shoe 39 ofeach assembly is provided with a copper strip 40 moulded within theouter end of the shoe or brush and extends around the side edge of thecontact arm and over its face and is fastened thereto by screws 40a, asshown in Fig. l. A hollow cylindrical spring holder 4| of brass isprovided with a rounded reduced end 4 la which projects into a centralhole in the shoe. A coiled spring 42 within the holder seats at one endagainst the inner portion of the holder and at its other end passesthrough a hole in the contact arm and seats against a strap of metal 43serving as a stop. This strap is secured to the face of the contact armby the screws 43a. The spring holder is freely movable and guided in itsmovement against the collector ring by a cylindrical guide 44,preferably made of steel tubing and fixed at one end to the contact arm.

The contact arm is actuated by a drive arm 45 of sheet steel. It isfixed to the end of the drive shaft by brazing or staking. At oppositeends bf the drive arm are carried bushings IE or moulded insulation, theinner portions of which pass into openings in the contact arm. On theinner face of the contact arm are mica washers 41 covered by steelwashers 4B. Rivets 49 pass through the bushings 46 and the washers andhave their inner ends spun over the washers 48 for fastening thepartstogether. One end of the drive arm is bent outwardly at 45a and a metalclip 451) with an outwardly extending end is welded to thedrive armforthe purpose of coupling the device to another similar device forsimultaneous operation when desired.

On the end of the contact arm opposite the brush assembly end and on theinside of the arm is fixed by screws 50a a counter-weight 50 of sheetbrass, lead or other material. Its weight is made such that the contactarm and parts associated therewith are mechanically balanced on oppositesides of the drive shaft. This balanced relationship results in the sameforce being exerted to move the parts, regardless of their adjustedposition, and also eliminates any selfmovement of the arm due tounbalanced gravitational forces.

It is apparent from the foregoing description that the central shaft [3serves to hold the contact arm and drive arm in their proper axialposition with reference to the contact segments and collector ring. Thispermits simplicity and ease of assembling and mounting these parts andlikewise permits convenient dissembling for inspection, cleaning and therenewal of the brushes by merely removing the end nut 14b and the crosspin Ida and the pulley M. The shaft I3 together with the drive arm,contact arm and brushes may then be withdrawn as a unit from the rear ofthe device.

The central space is open for ventilation and the free dissipation ofheat. The embedding of a portion of the winding and of the resistors 9and segments 8 and their connections in the insulating material l2 fullyprotects them and gives excellent heat conduction from them to the metalbase plate I and to the metal cup II.

The provision of two contact shoes or brushes which engage the collectorring on opposite sides of and spaced equi-distant from the longitudinalcenter line of the contact arm together with the approximate center lineposition of the brushes which engage the contact segments, serves toavoid any sidewise tipping of the contact arm, or tendency to turn onits longitudinal axis when moved. This aids in obtaining smooth movementof the brushes and contact shoes on their engaged surfaces and maintainsthe lever in its plane of rotation.

It will be noted that the brushes engaging the contact segments are at agreater distance from the axis of the central shaft than the contactshoes which engage the collector ring. The combined pressure of theshoes against the collector ring is made greater than that of thebrushes against the segments in approximately the inverse ratio of theirdistances from the axis of the shaft by the design of the springsengaging the brushes and shoes. This gives a condition that the combinedpressure of the contact shoes engaging the collector ring times theirdistance from the central axis approximately equals the combinedpressure of the brushes engaging the segments times their distance fromthe central axis. Thus the turning force to overcome the friction of thebrushes and shoes in their movement is approximately equal on oppositesides of the contact arm which avoids any unbalanced turning strain onthe contactarm and actuating shaft. It should also be 'noted'that thedistance from the bearing surface of the collector ring to the contactarm is less than the distance from the surface of the segments to thecontact arm. In view of the pressure of the collector ring contactsexceeding the pressure of the segment contacts, the tendency to tip thecontact arm in overcoming the frictional contact of the engagingsurfaces when the arm is rotated is thus greatly reduced. Thisapproaches the ideal condition in this respect of having the moment ofthe frictional resistance of the collector ring contacts with referenceto the distance of their contact faces from the contact arm equal to themoment of the frictional resistance of the segment brushes withreference to the distance of their contact faces from the contact arm.

Although a particular embodiment of this improvement has been describedand shown, it will be understood that various modifications may be madewithout departing from the scope thereof.

I claim:

1. Electric controlling apparatus comprising a circular core, a windingthereon, a series of fixed contact segments extending outwardly andradially from the winding, a series of resistors electrically connectedbetween said segments and turns of the winding respectively andpositioned under said segments, common means for supporting saidsegments, resistors and winding in fixed relation to each other, andmovable contact means for successively engaging said segments.

2. Electric controlling apparatus comprising a.

circular core, a winding thereon, a series of fixed contact segmentsextending outwardly and radially from the winding, a series of resistorselectrically connected between said segments and turns of the windingrespectively, insulating material for embedding said resistors and atleast partially embedding said winding and segments in fixed relation toeach other, and movable contact means for successively engaging saidsegments.

3. Electric controlling apparatus comprising a core, a winding thereon,a series of fixed contact segments extending outwardly from the winding,a series of resistors electrically connected between said segments andturns of the winding respectively, insulating material for embeddingsaid resistors and at least partially embedding said winding andsegments in fixed relation to each other, said resistors beingpositioned under said segments, and movable contact means forsuccessively engaging said segments.

4. Electric controlling apparatus comprising a circular core, a windingthereon, a circular base plate with a retaining rim, a series of fixedcon tact segments extending outwardly from the winding, a series ofresistors electrically connected between said segments and turns of thewinding respectively, insulating material on said base plate embeddingsaid resistors and at least partially embedding said winding and.segments, and movable contact means for successively engaging saidsegments.

5. Electric controllin apparatus comprising a circular core, a windingthereon, a circular base plate with a retaining rim, a series of fixedcontact segments extending outwardly from the winding, a series ofresistors electrically connected between said segments and turns of thewinding respectively, insulating material on said base plate embeddinsaid resistors and at least partially embedding said winding andsegments, said resistors being positioned under said-segments, andmovable contact means for successively engaging said segments.

6. Electric controlling apparatus comprising a circular core, a windingthereon, a circular base plate with a retaining rim, a series of fixedcontact segments extending outwardly from the winding, a series ofresistors electrically connected between said segments and turns of thewinding respectively, insulating material on said base plate embeddingsaid resistors and at least partially embedding said Winding andsegments, a retainer extending within the winding at the central portionof the base plate for providing an open central space and for retainingsaid insulating material from the central space, and

movable contact means for successively engagln said segments. 7

RUFUS A. ANDREWS.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

